If you haven’t heard Subway has three federal class-action lawsuits claiming their footlong comes up short.
With Stephen Colbert jumping all over the “Scamwich“, I thought it would make an interesting math task.
Show the Colbert clip which features the journalistic reporting by the New York Post. Kids could do the math to discover how the Post calculated if customers “buy a $7 ‘footlong’ every other day for a year, an axed extra inch adds up to a loss of roughly $100.”
Question: How did the New York Post calculate a loss of $100?
What information is useful?
- one twelfth of $7.00 is 0.583
- every other day for a year is 182 days.
Is this truly the loss? Have students read Chicago Tribune’s Eric Zorn article because he calculates it differently. He says the meat and cheese are pre-measured, so the same amount that goes into an 11-inch footlong goes into a 12-inch footlong. According to Zorn, customers are only being cheated by 8 percent of the bun, or 42 cents on a $5 sub.
Perhaps Zorn and the NY Post are both wrong. If Zorn’s assumption is correct, wouldn’t it be logical to also assume bread loaves are pre-measured as well? If so, the customer is still getting the same amount of bread. Therefore he is not being cheated.
What a great conversation to have with the kids.
Students completed the task this week and students gave me tremendous insight into their mathematical thinking. Some were spot on, others had serious mistakes. The NY Post calculations were challenging for many students. I showed the Colbert clip, but stopped it at the point when the problem was posed. I posted the problem on the projector and the students worked in groups. A few argued the need to divide $7 by 11 because the customer only got 11 inches. MANY took 12 and divided it by 7 to get a per inch cost of $1.71. They didn’t check for reasonableness! A few thought to multiply $7 by 182 footlongs but that was their final answer. And a couple of students were very perplexed by the problem and had little understanding as to how to approach it.
Nearly everyone liked the “current events” and real world application. When I suggested that perhaps no customers are being cheated because the ingredients are pre-measured, one student wrote on the exit slip, “All that work and it really didn’t matter.” At the end of class I cleared up that misconception!